What is Netcat?

Netcat is a flexible network utility for network access to ports on computer systems. It can connect to a variety of ports, by either TCP or UDP. For PPC LinkStation owners with UBoot installed, it provides one with the means to do a variety of tasks, including controlling the boot process, altering environmental variables, and flashing data/images to ROM. The official site for Netcat is here.

Getting Netcat and Installing it for Use with UBoot & LinkStations

Netcat for:

Windows

OS X (included in Tiger 10.4)

Linux (already included in many Linux distros)

Using Netcat w/ UBoot to control the boot process

First, get your network adjusted so that the ip addresses are what UBoot expects them to be. Your desktop/laptop must have an IP address of 192.168.11.149. Your LS needs to be at 192.168.11.150. The network should be 192.168.11.0 and the subnet mask 255.255.255.0, though these last two seem to take care of themselves. (Note: If your version of UBoot was custom made with a different IP range for a network like 10.0.1.0, then adjust accordingly.)

To connect to your UBoot-equipped LS during its boot process, do the following almost simultaneously:

execute the following command

nc -u -p 6666 -v 192.168.11.150 6666

right after that (within seconds) turn your LS on and wait for something like this to appear:

It is possible to chose which of these three mode you boot into by passing boot arguements to specify which kernel and which file system you want. (A slightly easier but much less instructive way will be pointed out at the end.) These three examples are for illustrative purposes, not because they are the easiest way.

Note:The easy way to do these from the UBoot command line is with bootcmd3, bootcmd2 and bootcmd1, as these are values that were predefined by LinuxNotIncluded. Read the output of

?

for more details on the default env var values.

Changing Environment Variables for Network Convenience

The version of UBoot that I downloaded and installed for my HG and KuroHG has the 192.168.11.x setup as its defaults. Since my home network is set up with 10.0.1.x IP addresses, I decided to use Netcat and UBoot to change my env vars so that I wouldn't have to switch the KuroHG (my lab rat) to the 2nd port on my computer (with 192.168.11.x address). I could just leave it on the main network all of the time, and get Netcat-UBoot control whenever I wanted it.

The original Network env vars were these:

ipaddr=192.168.11.150
serverip=192.168.11.149
ncip=192.168.11.149

To change these and make the new values persistent, I did the following:

which basically makes a mini-script of four commands. The name of the env var was then changeip, and its value was a sequence of four commands. The first three commands would set new IP addresses as I wanted, and the last command (saveenv) would make all the current env var values persistent. To execute it, I just did:

run changeip

I lost my connection (expected) but when I rebooted the KuroHG attached to the 10.0.1.0 network, it came up where I wanted it to be: